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Northern Black Widow (Lactrodectus variolus)


Detailing the physical features, habits, territorial reach and other identifying qualities of the Northern Black Widow.

 Updated: 2/17/2019; Authored By Staff Writer; Content ¬©www.InsectIdentification.org




The Northern Black Widow shares a lot in common with its southern cousin, including a painful bite that only feels worse, meriting an urgent visit to the doctor.



The glossy, black abdomen of the Northern Black Widow is dotted with large red circles on the dorsal (back) side. A split, or 'broken', red hourglass is clearly visible on the ventral (belly) side. Noting that separation between the top and bottom the the hourglass is important. It is different from the solid, one-piece hourglass seen on the more widely-recognized Southern Black Widow. The 'broken' hourglass means the spider is NOT a Southern Black Widow. The venom of both types of Black Widow females is toxic, but the Northern Black Widow's is less so. Only females are harmful; males are slightly different in pattern and are considered harmless.

Mortality from a bite by a Northern Black Widow is about 1% of all victims, with most of those fatalities being small children. Any bite from a Northern Black Widow merits a visit to a physician as it is difficult to gauge how toxic the spider's venom is at the time of the bite and how each individual will respond to it. (i.e. A spider that recently emptied venom into an insect will have less venom in a bite given soon after that.) All bite victims experience immediate pain, and it increases in intensity for hours afterward. It usually subsides in a day. Other symptoms include sweating, fever, nausea, rapid heart rate, and weakness. A physician can help ease the immediate discomfort a victim feels and monitor the patient for other symptoms until a full recovery is made.

This species of spider forms tangled, messy webs in woodlands, stone and wood piles, and undisturbed corners of sheds, garages and other shelters outside. It is not aggressive and does not actively seek to bite people. The Northern Black Widow is shy and more apt to try and hide. If startled or threatened, which can happen when a person suddenly turns over the log or stone the spider is sitting on, it bites in defense. Sightings of this species are somewhat rare as it is active at night and less likely to be seen during daytime. If spotted, treat it as a dangerous spider and keep your distance.
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Taxonomic Hierarchy
Kingdom: Animalia
  Phylum: Arthropoda
    Class: Arachnida
      Order: Araneae
        Family: Theridiidae
          Genus: Lactrodectus
            Species: variolus
Identifying Information
Scientific Name: Lactrodectus variolus
Category: Spider
Size (Adult; Length): 4mm to 11mm (0.16in to 0.43in)
Colorwheel Graphic Colors: black, red, orange, white
Descriptors: biting, painful, venomous, harmful
Territorial Map
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Territorial Reach (A-to-Z)
Alabama
Alaska
Arizona
Arkansas
California
Colorado
Connecticut
Delaware
Florida
Georgia
Hawaii
Idaho
Illinois
Indiana
Iowa
Kansas
Kentucky
Louisiana
Maine
Maryland
Massachusetts
Michigan
Minnesota
Mississippi
Missouri
Montana
Nebraska
Nevada
New Hampshire
New Jersey
New Mexico
New York
North Carolina
North Dakota
Ohio
Oklahoma
Oregon
Pennsylvania
Rhode Island
South Carolina
South Dakota
Tennessee
Texas
Utah
Vermont
Virginia
Washington
West Virginia
Wisconsin
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Alberta
British Columbia
Manitoba
New Brunswick
Newfoundland and Labrador
Nova Scotia
Ontario
Prince Edward Island
Quebec
Saskatchewan
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Mexico
Note: An insect's reach is not limited by lines drawn on a map and therefore species may appear in areas, regions and/or states beyond those listed above as they are driven by environmental factors (such as climate change), available food supplies and mating patterns. Grayed-out selections indicate that the subject in question has not been reported in that particular territory. U.S. states and Canadian provinces / territories are clickable to their respective bug listings.


Spider Anatomy
Graphic showing basic parts of spider anatomy
1
Legs: Spiders have four pairs of legs and these are attached to the cephalothorax.
2
Pedipalps: Small appendages near the mouth used as taste and smell organs.
3
Cephalothorax: Contains eyes, head, mouthparts, and legs.
4
Abdomen: Contains various organs related to digestion, reproduction, and web-making.
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Spinnerets: Used in the production of spider silk for fashioning webs or catching prey.
NOTE: Unlike insects, spiders have both an endoskeleton (internal) and exoskeleton (external).